Call delivery is the process by which a call is placed to a telephone subscriber. When a call is placed to a subscriber's telephone number or address, the telephone system automatically delivers the call to the subscriber's registered terminal. Terminal is a term of art that reflects the growing number of devices that can be connected to a telephone network. The cellular telephone, or cell phone, is one example of a terminal.
Many different types of telephone networks can execute call delivery, a function once done exclusively by traditional hard-wired (landline) networks. Typical of such different types of telephone networks include cellular telephone networks and Internet-based telephone networks. Internet telephony is one of the newest forms of telephone networking. In Internet telephony, calls are converted to digital signals according to protocols and standards that are suitable for connecting terminals and completing telephone calls via connections to the Internet. Various industry standards and terms of art have evolved to describe the different networks and methods of call delivery. The glossary found at the end of the specification defines many of these terms.
Call Forwarding is a standard service in telephone networks. A subscriber tells her service provider that, under certain conditions, if a call cannot be successfully placed to her terminal, it should instead be forwarded to another location. For example, a user could ask that her calls be forwarded to a co-worker when her cellular phone is busy. Most wireline, wireless and Internet telephone networks have mechanisms that are designed to provide these services. They work adequately when the originating system, the user's current terminal, and the destination terminal are all in the same network. However, they do not work as well when calls are being inter-worked, that is, connected between different types of networks that use different protocols for call forwarding. For example, call forwarding generally does not work when a call is placed using one system, the user is roaming in a second and the forwarded-to number is located in a third network.
Accordingly, there is a need for a generalized method and system to seamlessly and reliably complete call forwarding connections across a plurality of networks of differing types including traditional wireline networks, wireless networks, and the ever-growing number of Internet-based telephone networks.